• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.267-277
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• 2009

Partial safety factors of the load, resistance, and reliability function are evaluated according to the target probability of failure on sliding mode of monolithical vertical caisson of composite breakwaters. After reliability function is formulated for sliding failure mode of caisson of composite breakwaters regarding bias of wave force, uncertainties of random variables related to loads, strengths are analyzed. Reliability analysis for the various conditions of water depth, geometric, and wave conditions is performed using Level II AFDA model for the sliding failure. Furthermore, the reliability model is also applied to the real caisson of composite breakwaters of Daesan, Dong- hae, and Pohang harbor. By comparing the required width of caisson of composite breakwater according to target probability of failure with the other results, the partial safety factors evaluated in this study are calibrated straightforwardly. Even though showing a little difference on the 1% of target probability, it may be found that the present results agree well with the other results in every other target probability of failure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.197-205
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• 1992

For the optimal design of composite breakwaters, a computer program PROCOBRA is developed using the combined ALM-BFGS algorithm. A model formulation for the section design optimization problem of composite breakwaters is proposed where a concept of subsectional weighting factors is introduced in the objective function. Usability of the program is verified through a numerical example. From the study, it is found that the ALM-BFGS method is reliable and can be effectively applied for the design optimization of coastal structures. Compared with conventional design process, it is proved that the economical design of composite breakwaters is possible.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.2
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• pp.92-100
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• 1992

플렉시블한 관절을 가지고 있는 로보트에 대하여 계단(step) 혹은 경사(ramp) 함수로 기준입력이 주어졌을 때, 모델의 불확실성이나 외란 아래에서 추적오차가 없는 디지찰 제어기법을 제시하고 실제로 실험을 통하여 제어기를 MC 68000으로 구현함으로써 제안한 제어 알고리즘의 유용성을 보였다. 제어기 설계에 있 어서 고려한 사항들은 비선형 마찰력, 중력에 의한 외란, 구동기와 부하사이의 뒤틀림 스프링 효과, 구리고 측 정할 수 없는 상태변수들이다. 또한 미분불가능한 쿨롱마찰로 인하여 전체 시스템이 이산/연속 혼성 시스템이 되어 출력에서 나타나는 리미트 싸이클을 해석/추정하기 위하여 혼성 시스템에서의 기술함수(Describing Function) 법을 제시하였다.

• Journal of KIISE:Software and Applications
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• v.27 no.12
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• pp.1227-1237
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• 2000

Hindley/Milner let-다형성 타입체계(let-polymorphic type system)에는 두 가지 타입 유추(type-inference) 알고리즘이 있다. 하나는 표준으로 알려진 W 알고리즘으로 프로그램의 문맥에 상관없이 상향식으로 유추하는 알고리즘이고, 다른 하나는 프로그램의 문맥에 따라 하양식으로 유추하는 M 알고리즘이다. 본 연구에서는 함수 적용(application)이 중첩되는 경우, M 알고리즘에 병목현상이 발생함을 보이고, 이러한 병목현상이 발생하지 않는 혼성 알고리즘 H를 제시한다. H 알고리즘은 M 알고리즘을 함수 적용 부분만 W 알고리즘으로 변형한 알고리즘으로, W보다 일찍 M보다는 늦게 오류를 감지함을 보인다.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.29-41
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• 2018

Separating a mixture having an azeotrope or low relative volatility with single distillation column is difficult. Separating water-acetic acid mixture and water-ethanol mixture with a distillation column consumes a lot of energy. Pervaporation membrane can be used to separate the mixture in the concentration region where separation is difficult with distillation. We simulated a distillation-membrane hybrid process where membrane is located on the head of the distillation column for efficient separation of water-acetic acid and water-ethanol mixture. Permeability data were obtained from experiments and literature. We formulated an optimization problem for the process with total annual cost (TAC) as an objective function and major design variables as optimization variables. Major optimization variable affecting TAC of the hybrid process was shown to be distillate concentration. We also suggested a simplified optimization procedure to get a close-to-optimal solution.

• Journal of the Korean Chemical Society
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• v.67 no.1
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• pp.13-18
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• 2023

We evaluate electron density functional theories for the computation of 0-1 and 1-2 transition energies of local OH stretching motion of water molecules in condensed phases. By examining thirteen density functionals and nine sets of basis functions, it was found that the optimal combination that predicts the transition energies highly correlated with those calculated by the coupled cluster theory, CCSD(T), is the hybrid density functional theory developed by Head-Gordon group, ωB97X(D)/6-31+G^*.

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.198-205
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• 1979

A valence bond method of calculation of the dipole moments for octahedral $(M(III)0_3S_3)$ type complexes are developed, using $d^2sp^3 $hybrid orbitals of the central metal ions and the single basis set orbital of ligands. (M (III) =V (III), Cr (III), Mn (III), Fe (III), Co (III), Ru (III), Rh (III) and OS (III)). In this method the mixing coefficient of the valence basis sets for the central metal ion with the appropriate ligand orbitals is not required to be the same, differently from the molecular orbital method. The valence bond method is much more easier to calculate the dipole moments for octahedral complexes than the approximate molecular orbital method and the calculated results are also in the range of the experimental vaues.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.227-238
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• 1997

다목적함수 최적화를 효과적으로 수행하기 위하여 유전자 알고리즘과 직접탐색법을 결합하여 혼성형 최적화기법을 구현하였다. 이 방법은 유전자 알고리즘을 사용하여 최적점이 존재할 가능성이 높은 영역을 탐색한 후, 이 영역에서 직접탐색법을 사용하여 최종해를 찾는다. 따라서 탐색의 효율을 향상시키고 계산시간을 절약할 수 있는 장점이 있다. 그러나 최적화기법이 효율적이지만, 최적화기법을 사용하기 위해서는 전문가의 전문지식이 필요하다. 따라서 실제 최적화를 수행하기 위해서는 관련 분야의 전문지식과 최적화기법이 효율적으로 결합되는 것이 필요하다.

• Journal of the KSME
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• v.34 no.5
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• pp.372-383
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• 1994

복합재료의 피로특성과 해석방법에 대하여 간략하게 살펴보았다. 복합재료의 피로현상에 대한 이해의 폭이 넓어짐에 따라 앞에서 소개한 방법외에 파단모드별 연구, 역학에 기초를 둔 해석법, 유한요소법의 적용, 혼성복합재료(hybrid composites)의 피로수명 예측 등의 다양한 연구가 진 행중이나, 아직 정립된 피로수명 예측식은 없다고 말할 수 있다. 재료의 손상을 나타내는 매개 변수로서 강성변화의 유용성이 밝혀진 상태이므로 앞으로 이를 이용하여 실제의 현상을 표현할 수 있는 손상함수의 구성과 피로수명 예측에 관한 연구가 수행되어야 한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.4
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• pp.336-343
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• 2004

This paper reports the first known free vibration data for thin rectangular plates with V-notches. The classical Ritz method is employed with two sets of admissible functions assumed for the transverse vibratory displacements. These sets include (1) mathematically complete algebraic-trigonometric polynomials which guarantee convergence to exact frequencies as sufficient terms are retained, and (2) corner functions which account for the bending moment singularities at the sharp reentrant corner of the Y-notch. Extensive convergence studies summarized herein confirm that the corner functions substantially enhance the convergence and accuracy of nondirectional frequencies for rectangular plates having the V-notch. In this paper, accurate frequencies and normalized contours of vibratory transverse displacement are presented for various notched plates, so that the effect of corner stress singularities may be understood.